Hardwood-based laminated wood flooring is a popular product used in truck trailers because of its performance and the many advantages it offers. The surface characteristics of hardwoods such as high wear resistance and slip resistance are most desirable. The strength and stiffness of the flooring is important for efficient and safe transfer of the applied loads to the cross-members of the trailer. The shock resistance of wood is useful to withstand any sudden dropping of heavy cargo on the floor. Nail holding capability and the ability to absorb small amounts of water, oil or grease without significantly affecting slip resistance are yet additional favorable properties of hardwood flooring.
The hardwood-based laminated floor unfortunately also suffers some disadvantages. Under proper and normal conditions, a hardwood laminated floor has a life expectancy of 10, 15, and even 20 years of good service. However, if conditions exist, the development of wood-degrading organisms, like fungi, can also occur and the floor will eventually fail prematurely.
The existence and development of rot caused by fungus in laminated wood trailer flooring depends on the moisture conditions of the wood. Wood decay only occurs when the moisture content of the wood is above the fiber saturation point (usually between 25% to 30%). It is recognized by the wood industry that wood having a moisture content below 20% will not decay. In normal conditions, the moisture content of a laminated wood floor in the United States will vary between 12% to 17%. At this moisture level, decay will not form.
Most problems with decay on a laminated wood trailer floor or container will occur at the back of the trailer or the container, near the rear doors. Because the trailer doors are often open in that area, the floor is exposed to outside conditions. The outside conditions by themselves are not a problem: it is not because it rains on a wooden floor, that the wood will automatically develop fungus. The problem is more related to the design of the trailer or the container. In some trailers or containers, a threshold plate made of a steel diamond plate, which covers the first 1 to 4 feet of the wooden floor is often used. The threshold plate's purpose is to protect the wood floor from the impact of a fork lift when it enters the trailer. The threshold plate also to protects and reinforces the wooden floor at the rear of the trailer.
The problem with the threshold plate is that when it rains (or snows) and the rear doors are open, the water travels over the top of the threshold plate and ingresses between the edges of the steel plate and the wooden floor. The water stays trapped and cannot evaporate because of the threshold plate covering it. Thus, the moisture in the wood starts to increase until it reaches a level where fungus starts to grow, and decay will eventually form. FIG. 1 shows an 11 year old laminated oak floor with severe fungus attack and wood rot. Of course, FIG. 1 shows a floor with the steel diamond plate removed.
Some solutions have been proposed to combat this problem. Pressure treatments using oxide copper (like copper-8) have been used to protect the wooden floor from fungi and wood decay. This method is very effective but also very expensive (50 to 75 cents per square foot). However, because of environmental concerns, this product can no longer be used.
Some trailer manufacturers have changed the design of their trailers and are no longer using hardwood flooring for the first 2-3′ of floor at the rear. Instead, they use a metal structure with no wood underneath. This solution is also very expensive, and increases the weight of the trailer and reduces the load capacity of the trailer.